This publication was originally prepared as a review paper for the 1999 Eastern Region International Plant Propagator's
Society meeting. It will be published in the IPPS Combined Proceedings Volume 49, 1999.

INTRODUCTION

Hostas are a group of popular shade tolerant herbaceous perennials known more for their foliage effects than for their
flowering characteristics. Increased market demand by consumers due in part to the long market window of a plant sold
primarily for its attractive foliage, and the number of cultivars available, has resulted in limited supplies of popular cultivars.

Hosta taxa are commonly propagated by division or tissue culture. Sexual propagation is used by hybridizers to develop new
cultivars, but is not a commercially viable propagation method because seed propagation does not produce a plant identical
to the parent. Hostas are slow growing (Armitage, 1997) and simple division does not produce adequate numbers of new
plants. "Mowing" and "The Ross Method" (Grenfell, 1996) and the application of benzyladenine (BA) (Garner, et al.,1995,
1996, 1997; Hoover, et al., 1998; Keever 1995; Keever, et al.1995a, 1995b; Keever and Brass, 1998; Schultz, et al.,1998)
increase the number of offsets resulting in a greater number of divisions that are identical to the mother plant. Tissue culture
has been able to propagate large numbers of plants, but it's use as a propagation technique requires fastidious care in both
the technique and evaluating the product of that technique.

DIVISION

Division is the primary means of propagating hosta. Field grown plants are traditionally dug and divided in the spring when
the shoots are dormant or less that 1 inch (2.5 cm) (Nau, 1996). The third Spring of growth is when the greatest number of
divisions occurs (Aden, 1990a). Most think of division as the separating of shoots with roots, but it is possible to remove
the terminal shoot or dormant bud and further divide to a plant having a single lateral bud and a root or rhizome (Summers,
1969). As this results in significant wounds there is an increased chance of disease.

Amateur gardeners divide in the spring, but to maintain a good landscape appearance may separate the division away from
the mother plant with a sharp trowel or knife without removing the mother plant from its site. Even though spring division is
considered the optimum time to produce a quality containerized plant for market in a relatively short time of 2-5 weeks
(Nau, 1996), nurseries may divide to fill an order anytime (Summers, 1969). It seems hostas are frequently divided from late
winter through fall (Davis, 1998). Diana Grenfell recommends removal of leaves from plants divided in the Summer
(Grenfell, 1996). David Beattie recommends a reduction in leaf area and shade whenever dividing after the leaves have fully
expanded (Beattie, 1996). Older plants tend to be more difficult to divide (Gear, 1996). While young plants and certain
cultivars are easily pulled apart, knives or pruners are sometimes needed to cut divisions apart. Selecting large vigorous
plants to maintain as mother plants (Davis, 1998) rather than smaller plants typically used ( Keever et al., 1995b) will result
in more divisions, as will, proper care and providing a good growing environment.

TECHNIQUES TO INCREASE THE NUMBER OF DIVISIONS

Hosta do not naturally produce a large number of shoots that can be harvested. This limitation has forced the development
of several methods to increase the number of potential divisions. The objective of increasing the number of divisions is to be
able to sell more plants but increasing the size of plants in the landscape is desirable as well.

The first method to increase the number of divisions is "mowing" the plants down to approximately .5 inches (1.25 cm)
during the summer forcing buds to break and increasing the number of shoots. The second, "Ross-izing" or the "Ross
Method", is described as cutting through the stem just above the basal plate down through the basal plate to the roots and
then making a similar cut at 90 degrees to the first, essentially quartering the plant in the late spring or early summer (Ross,
1982, Zumbar, 1991). Additional shoots will develop at the cuts. The third method is apply benzyladenine, a cytokinin, as a
foliar spray or drench to the plants (Garner, et al.,1995, 1996, 1997; Hoover, et al., 1998; Keever, et al., 1995; Keever, et
al, 1995a, 1995b; Keever and Brass, 1998; Schultz, et al.,1998) to increase offset formation. In several studies the
application of BA resulted in offset formation when the controls produced no offsets. Researchers have used the synthetic
cytokinin Pro-shear (BA) in several of their studies and found it to be effective in increasing the number of offsets formed,
but consistent results have not been found for all cultivars (Garner, et al.,1995).

N-6-benzylaminopurine (BAP-10) has been shown to be effective in increasing offsets in 11 hosta cultivars (Hoover et al.,
1998) The presence of offsets at the time of BA application resulted in fewer offsets being produced compared to plants
with no offsets at the time of a BA application (Keever and Brass, 1998). Keever, et al., (1995b) reported that the stage of
development of the offsets resulting from cytokinin treatments affected the rooting of the stem cuttings. Those offsets with
2 or more leaves unfurled rooted more readily that those with less unfurled leaves. It would appear that a program
developed around the research on BA treatments to increase offset formation would benefit hosta propagators.

SEED PROPAGATION

Hosta species can be propagated by seed, however, sexual propagation is mostly limited to producing plants from seed
resulting from selected crosses by hosta hybridizers. Methods of hybridizing hosta, including: selecting parents, the
handling and storage of pollen, making the cross, and producing plants from seed are described in The Gardener's Guide to
Growing Hosta by Diana Grenfell (1996) and The Hosta Book, Second Edition edited and compiled by Paul Aden (1990b).
Rarely does a good variegated hosta cultivar result from uncontrolled pollination (Micheletti, 1996).

Once seed has been produced it can be directly planted or stored in a cool dry environment for a short term or in a
refrigerator for a longer term. Hosta seed viability varies greatly (Aden, 1990b). Direct seeding of important crosses would
be recommended until a hybridizer gets to know the seed characteristics of his/her crosses.

Seed are broadcast on a fine textured medium, kept moist and at 60-75oF (16-24oC) in order to achieve good germination.
Light will be needed once the true leaves appear. Hybridizers and amateur gardeners alike must be diligent in culling out the
unacceptable seedlings. The use of hosta standards (similar cultivars currently available) for comparison will help in the
selection of quality species plants and new cultivars.

TISSUE CULTURE

Considering the slow production of plants by division, it became inevitable that tissue culture would (and does) play a
critical role in the propagation of hosta. Tissue culture has made it possible for hostas to be in every landscape. Many new
cultivars are propagated by tissue culture. A recurring criticism of tissue culture for hosta propagation has been the
production of plants are produced that are not true to type and the older the culture gets the more likely there will be
"sports". Meyer (1980) found that when 'Francis Williams', a popular cultivar, was propagated by tissue culture only 45%
of the plants produced were variegated, with the rest being 45% a gold sport and 10% a green sport. These kinds of early
results with tissue culture of hosta were discouraging and resulted in resistance to tissue- cultured plants in the market. In
order to have a successful tissue-culture program with hosta it is important to be able to identify the form of the cultivar at
roguing. The purchaser of tissue cultured plants should be able to evaluate the plants they receive to ensure the plants they
invest in are true to cultivar. It can take 4 to 5 years before hosta taxa reach maturity of form and color (Armitage 1997).
Establishing standards (plants known to be true to the cultivar grown to the same stage of development) to use to compare
plants at different stages of growth in order to rogue several times through the production cycle is important. The source of
the tissue to be cultured, florets, flower scapes, or shoot tips can make a difference in maintenance of parent plant
characteristics, as can environmental treatments (Papachatzi, et al., 1981). Certain environments and production factors can
affect the variegation or form of a plant in nursery production or in the landscape. A loss of variegation can occur in areas
of high temperatures when nitrogen fertilizers are used (Armitage, 1997) causing plants to be mistakenly thought not true to
type. Considering the precise and fastidious care required to propagate hosta in tissue culture the commercial success of this
technique is a tribute to those propagators that produce vigorous, disease-free, true-to-name plants.

CONCLUSIONS

Tissue-culture techniques will continue to be refined by both large and small commercial laboratories to eliminate deviant
plants from the production cycle and, ultimately, from getting to the consumer. Division will be the propagation method of
choice for hosta, especially for small nurseries and specialty nurseries that sell a few plants of many different cultivars. It
would seem that treatments and cultural practices that increase offset formation would benefit the propagator, the nursery
grower, and the landscaper.

It would be interesting to know if commercial propagators and nurserymen have adopted the application of BA products to
increase Hosta offset formation.